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| United States Patent |
5,567,462
|
|
Ehrlich
|
October 22, 1996
|
Pecto-cellulosic product from whole citrus peel and other materials
Abstract
Pecto-cellulosic compositions are prepared by treating comminuted citrus
peel or other pectin-containing material in an acidified aqueous solution
to solubilize pectin. The pectin is then recovered in the cellulosic
matrix of the citrus peel by adjusting the pH of the solution and dried.
The resulting pecto-cellulosic product is incorporated in food and other
products.
| Inventors:
|
Ehrlich; Robert M. (North Hollywood, CA)
|
| Assignee:
|
Sanofi Bio-Industries, Inc. (Trevose, PA)
|
| Appl. No.:
|
231626 |
| Filed:
|
April 22, 1994 |
| Current U.S. Class: |
426/425; 426/431 |
| Intern'l Class: |
A23L 001/6; A23L 001/052.4; A23L 001/308; A23L 001/025 |
| Field of Search: |
536/2
426/425,431
|
References Cited
U.S. Patent Documents
| 2020572 | Nov., 1935 | Platt | 536/2.
|
| 2022471 | Nov., 1935 | Leo.
| |
| 2132065 | Oct., 1938 | Wilson.
| |
| 2173260 | Sep., 1939 | Leo et al. | 536/2.
|
| 3982003 | Sep., 1976 | Mitchell et al.
| |
| 4143172 | Mar., 1979 | Mitchell.
| |
| 4831127 | May., 1989 | Weibel.
| |
| 4923981 | May., 1990 | Weibel et al.
| |
| 5275834 | Jan., 1994 | Thibault et al. | 426/577.
|
| Foreign Patent Documents |
| 258743 | Mar., 1988 | DE.
| |
| 1369198 | Oct., 1974 | GB.
| |
| 1508993 | Apr., 1978 | GB.
| |
| WO91/15517 | Oct., 1991 | WO.
| |
Other References
Szabo, CA 79:77139, Konzer V Paprikaip. Kut. Intez., Budapest, Hung.
(1972), (S) 181-6.
|
Primary Examiner: Mullis; Jeffrey C.
Attorney, Agent or Firm: Townsend and Townsend and Crew LLP
Parent Case Text
This is a continuation in part of U.S. application Ser. No. 07/832,131,
filed Feb. 6, 1992, now abandoned, which is incorporated herein by
reference.
Claims
What is claimed is:
1. A method for preparing pecto-cellulosic compositions from a
pectin-containing plant raw material without a step of alcohol
precipitation, said method comprising:
combining comminuted raw material with an acidified aqueous solution
comprising a food acid and incubating the comminuted raw material in the
acidified aqueous solution at less than about 50.degree. C. for about 8 to
about 24 hours, thereby producing a mixture comprising a solid phase
containing cellulosic components and a liquid phase containing solubilized
pectin;
pureeing the mixture, while the mixture is in the acidified aqueous
solution, thereby producing particles less than about 200 .mu.m;
partially neutralizing the pH of the mixture; and
drying the mixture, thereby producing pecto-cellulosic solids.
2. A method as in claim 1, wherein the raw material is selected from the
group consisting of citrus peel, sugar beet, apple, and sunflower.
3. A method as in claim 2, wherein the raw material is citrus peel.
4. A method as in claim 3, wherein the citrus peel is dried, before the
step of combining the raw material with the acidified aqueous solution.
5. A method as in claim 3, wherein the citrus peel is fresh and is
comminuted to a size from about 3/8 to 1/2 inch prior to combining in the
acidified aqueous solution.
6. A method as in claim 1, wherein the acidified aqueous solution has a pH
between about 2 and about 3.
7. The method of claim 1, wherein the acidified aqueous solution is
acidified with a food acid selected from the group consisting of
phosphoric acid, citric acid, and acetic acid.
8. A method as in claim 1, wherein the step of drying is carried out by
spray drying.
9. The method of claim 1, wherein the process steps are performed in a
batch mode.
10. The method of claim 1, wherein the process steps are performed in a
continuous mode.
11. A method for preparing pectin and pecto-cellulosic compositions from a
pectin-containing plant raw material without a step of alcohol
precipitation, said method comprising:
combining comminuted raw material in an acidified aqueous solution
comprising a food acid and incubating the comminuted raw material in the
acidified aqueous solution at less than about 50.degree. C. for about 8 to
about 24 hours, thereby producing a mixture comprising a solid phase
containing cellulosic components and a liquid phase containing solubilized
pectin;
pureeing the mixture, while the mixture is in the acidified aqueous
solution, thereby producing particles less than about 200 .mu.m;
separating the liquid phase from the solid phase;
partially neutralizing the pH of the liquid phase;
partially neutralizing the pH of the solid phase;
drying the liquid phase, thereby producing a pectin composition; and
drying the solid phase, thereby producing a pecto-cellulosic composition.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to pectin-containing compositions
and processes for their production. In particular, the present invention
relates to a process for preparing pecto-cellulosic compositions from
whole citrus peel.
Pectin is a natural colloid, frequently found in the plant world as a
component of cell walls, where together with other components, such as
hemicelluloses, it is linked to the cellulose and constitutes both the
structural tissue and the "cement" which gives rigidity to plant cells.
Pectin is present in all plant tissue, such as in apples and citrus
fruits, in variable quantities, as well as in some roots (beets, carrots),
tubers (potatoes), in sunflower heads, and elsewhere. Pectin has long been
used in the home for gelling jams using, for example, apple core or
quinces as the pectin source. Today, the fruit and confectionery industry
has used pectin widely for its gelling properties in acid and sugar media.
Other pectin properties, such as its gelling action in less acidic medium
and in the presence of calcium, thickening, colloidal suspension,
protection of casein, and the like, also contribute to the role of pectin
in the manufacture of food and pharmaceutical products.
Most commercially available pectins are purified to about 70% to 80% by
weight polyanhydrogalacturonic acid (AGA) and have a varying degree of
methoxylation (DM). High methoxyl pectins (DM above about 50%) form gels
at pH values below about 3.5 in the presence of sugar levels above about
60%. High DM pectins are typically used for gelling preserves and
confectionery foods. Low methoxyl pectins (DM between about 20% and 50%)
form gels at wider pH ranges in the absence of sugars, but require the
presence of divalent cations.
Commercial pectin is obtained from starting materials having a much lower
AGA content, such as dried citrus peel having an AGA content in the range
from about 20% to 30%. Extraction is achieved by hydrolysis, in warm
acidic medium, of protopectin to release the potentially soluble pectinic
acids from the cellulosic matrix in which they are initially included.
After separation of the cellulosic components, pectin is precipitated from
the resulting pectic juices, typically using an alcohol. The resulting
fibrous coagulum is alcohol washed, squeezed, vacuum dried, and then
ground in order to obtain a fine powder. The separated cellulose is a low
volume by-product which can be used, for example, as an animal feed
bulking agent.
Thus, it can be seen that the present method for producing commercial
pectin products can be expensive, both in capital expenditures and in
operating costs. Moreover, the present methods utilize only a portion of
the starting materials and result in waste or low value usage of the
cellulosic portions of the starting material.
For these reasons, it would be desirable to provide less costly methods and
processes for producing pectin compositions from starting materials, such
as whole citrus peels. Preferably, the methods could be implemented with
reduced capital expenditures (e.g., by requiring fewer processing steps)
and operating costs (e.g., by operating at ambient temperature). It would
be further desirable if the methods were able to incorporate a significant
percentage of the cellulose in the starting material in the final product.
Cellulose is an important part of dietary fiber and incorporation of the
final product would further enhance the economics of the method.
2. Description of the Background Art
East German Patent Application No. 258743 (Abstract) describes the
production of a pectin-like material for use with comminuted meats. The
pectin-containing material is produced from vegetables by comminution,
followed by acidification, neutralization, and mechanical dehydration.
U.S. Pat. Nos. 4,923,981 and 4,831,127, relate to the preparation of
"parenchymal cell" cellulose from pectin-containing materials, such as
sugar beet and citrus pulp. The materials are first treated with a strong
acid or a strong base at high temperatures for short periods of time to
release the cellulosic and hemi-cellulosic components thereof. The
treatment releases pectin from the starting materials without substantial
degradation. The starting material is subjected to physical shearing, and
the solid and liquid fractions of the treated mixture are separated and
utilized separately. U.S. Pat. No. 4,143,172 teaches the use of comminuted
citrus peel as a pectin material. U.S. Pat. No. 3,982,003, similarly
teaches the preparation of the pectin-like material by comminution of
citrus pulp, where the pulp is treated with a mild base in order to reduce
the degree of esterification. U.S. Pat. No. 2,452,750 teaches methods for
producing pectin by soaking comminuted citrus peel in a reagent which is a
nonsolvent for pectinous substances. U.S. Pat. No. 2,132,065, describes
hugh temperature, alkaline separation of pectin from citrus peel. U.S.
Pat. No. 2,022,471 discloses a process for making pectous materials using
a filter aid such as diatomaceous earth. International application, Pub.
No. WO 91/15517, describes methods for producing pectin-containing
products. British patent 1,369,198 describes a process for preparing
simulated fruit using a pectate sol. British patent 1,508,993 is related
to U.S. Pat. Nos. 3,982,003 and 4,143,172, described above.
The descriptions in each of the above references are incorporated herein by
reference.
SUMMARY OF THE INVENTION
Methods are provided for preparing pecto-cellulosic compositions from
citrus peel and other pectin-containing plant raw materials. The methods
utilize comminuted whole citrus peel, apple, sugar beet, sunflower, or the
like, as a starting material. The comminuted citrus peel is first combined
in an aqueous acidic or alkaline solution under conditions selected to at
least partially solubilize the pectin present in the raw material.
In some embodiments of the invention, solubilization is achieved by
exposure to a mineral acid (e.g., HNO.sub.3), at a pH in the range from
about 1 to 2.5 at room temperature. The comminuted material will remain
exposed to the acid for a time sufficient to result in a desired degree of
solubilization, typically for a period for at least about 16 hours. In
other embodiments, a "food acid" such as phosphoric acid is used at a pH
between about 2 and about 3. The solubilization step may also include
solubilization at an elevated temperature (e.g., above about 65.degree.
C.), for up to about three hours.
The pecto-cellulosic products of the invention are prepared from the
solubilized pectin without any prior separation step. The product can be
prepared using two ways. In one embodiment, the pectin is precipitated
back into the cellulosic matrix by adding a sufficient amount of an
alcohol to effect such precipitation. Typically, a final alcohol content
of at least about 60 weight percent is used. This
cellulose-alcohol-acid-water slurry is neutralized, and the alcohol and
water removed. Usually, the cellulosic matrix containing the precipitated
pectin is dehydrated by exposure to an alcohol wash, typically to a series
of successive alcohol washes having higher alcohol concentrations. The
compositions are usually further dried, typically by vacuum drying, prior
to grinding to the final desired size.
In other embodiments of the invention, the pecto-cellulosic product is
recovered without a precipitation step. In this method, the pH of the
comminuted material is adjusted to a more neutral range (e.g., by the
addition of base) and pureed, typically until particle sizes are less than
about 200 .mu.m, preferably about 150 .mu.m. The pureed material is then
spray dried, prior to grinding to the final desired size. Unlike alcohol
precipitated material, no residual alcohol is present in compositions made
using these methods.
The pecto-cellulosic compositions of the present invention will have a
weight percent of pectin (measured as polyanhydrogalactouronic acid using
the methods described below) from about 10 to 30, usually being from about
12 to about and 28, and often from about 15 to 20 based on the whole
product, including the cellulosic matrix. Such pecto-cellulosic
compositions have been found useful in the gelling of the aqueous phase of
various products. For example, compositions of the present invention may
be used in food products, such as jams, food spreads, confections, and the
like.
The compositions of the present invention are natural in that their
production does not require addition of any materials other than the
alcohols and acids described above. These materials are substantially
completely removed from the product prior to use. Additionally, the
pecto-cellulosic compositions incorporate natural fibers which are
valuable as dietary constituents. Surprisingly, it has been found that the
pecto-cellulosic compositions of the present invention appear to have a
greater gelling activity than commercial pectins. That is, the amount of
pectin in the pecto-cellulosic product of the present invention which is
required to obtain a desired level of gelling is in fact less than the
amount of commercial pectin which would be required to obtain the same
level of gelling.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a process flow schematic for a continuous process using alcohol
to precipitate pectin according to a method of the present invention.
FIG. 2 is a process flow schematic for a continuous process in which the
material is pureed and pH adjusted without the addition of alcohol.
FIG. 3 is process flow schematic for a continuous process in which the
material is separated into a liquid and solid phase before further
processing. This process leads to a pectin product and a pecto-cellulosic
product.
FIG. 4 is process flow schematic for a continuous process in which the
material is lixivated prior to further processing.
DESCRIPTION OF THE PREFERRED EMBODIMENT
According to the present invention, pecto-cellulosic compositions are
prepared from citrus peel and other pectin-containing plant raw materials.
Lemon peel is the preferred starting material, but orange peel, lime peel,
grapefruit peel, and other citrus fruit peels, as well as apple, sugar
beet, sunflower (flower portion of plant), and the like, may also find
use. Such citrus peels can conveniently be obtained from the citrus juice
industry after the juice and many of the essential oils have been removed
from the whole fruit. The citrus peel contains an outer, pigmented layer
referred to as the flavedo as well as an inner white layer referred to as
the albedo. Pectin is contained primarily in the albedo and sometimes the
flavedo will be removed prior to processing according to the present
invention. The other starting materials are also widely available.
The starting material in the present invention will be washed in order to
remove excess soluble materials and frequently will be dried, particularly
if the material is to be shipped to another location for processing.
Usually, if the material is not to be used when fresh, it will be suitably
treated to deactivate pectic enzymes which can degrade the
pecto-cellulosic product of the present invention.
The remainder of the specification will be directed specifically at the use
of citrus peel as a starting material, but the process conditions will be
generally suitable for any of the starting materials described above.
The citrus peel, when fresh, will be comminuted to a particle size below
about 1/2 inch, preferably below about 3/8 inch, prior to the treatment
steps described hereinbelow. The size of comminuted dry peel is less
critical. Comminuting can be performed in conventional size reduction
equipment, such as a hammermill, Rietz Disintegrator, Urschel Grinder, and
the like.
The comminuted citrus peel is first combined with an acid or alkaline
aqueous solution under conditions selected to at least partially
solubilize the pectin present in the comminuted peel. If an acid solution
is used, the pH of the resulting solution or slurry will typically be in
the range from about 1 to 2.5 pH. This can be achieved by addition of a
mineral acid, such as hydrochloric acid (HCl), sulfuric acid (H.sub.2
SO.sub.4), nitric acid (HNO.sub.3), and the like. When mineral acids are
used, the final pH will preferably be in the range from about 1.25 pH to
1.75 pH, usually about 1.4 pH to 1.5 pH.
Alternatively, "food acids" can be used such as phosphoric acid (H.sub.3
PO.sub.4), citric acid, acetic acid, and the like. Hydrolysis with these
acids usually occurs at a slightly higher pH. For phosphoric acid, the
lowest attainable pH is 2 pH to 2.1 pH. For citric acid the pH will be
about 3.2 to about 3.3, and slightly higher for acetic acid. One advantage
of using these acids to precipitate the pectin is that after
neutralization (with e.g., sodium hydroxide), phosphate, citrate and
acetate ions are present in the dried product. These ions increase the
solubility of the pectin by chelating multivalent metal ions (e.g.,
Ca.sup.+2) that tend to inhibit solubilization.
Alkaline hydrolysis is achieved by addition of an appropriate base such as
sodium hydroxide (NaOH), sodium carbonate (Na.sub.2 CO.sub.3, potassium
hydroxide (KOH), and the like. Alkaline hydrolysis is useful in producing
a pecto-cellulosic product with low methoxylation (DM less than about
45%).
The solubilization step is typically performed at a low temperature,
preferably below about 50.degree. C., more preferably below about
35.degree. C., and usually at ambient temperature. The solubilization step
will be carried out for a time sufficient to achieve the desired level of
solubilization, typically for a period of at least about 8 hours, more
preferably for a period of at least about 16 hours, and more preferably
for a period of about 24 hours, when the process is performed at ambient
temperature.
In some embodiments the solubilization step may also include hydrolysis at
an elevated temperature, usually above about 65.degree. C., preferably at
about 85.degree. C. to about 90.degree. C. Hot hydrolysis is typically
carried out for a period of at least about 1 hour, preferably less than
about 3 hours.
The acid or alkaline aqueous solution used in the solubilization step will
usually comprise water with a sufficient amount of the appropriate acid or
base to achieve the desired pH level. Optionally, the pectin may be
solubilized or hydrolyzed directly in acidified aqueous alcohol by
introducing the washed citrus peel into acidified aqueous alcohol without
initial solubilization in the acidified aqueous solution. The amount of
alcohol present in such a solubilization solution will usually be no
greater than about 40% by weight, preferably being no greater than about
30% by weight.
After the pectin solubilization has been achieved, at least a portion of
the solubilized pectin will be precipitated back into the cellulose matrix
of the citrus peel. Such precipitation can be achieved by increasing the
alcohol content of the solution. Suitable alcohols include methanol,
ethanol, isopropanol, and the like. These alcohols will be added to a
weight percent (based on the entire solution weight) of at least about
60%, and preferably to at least about 70%. Pectins are generally insoluble
in alcohols and such an increase in the alcohol content of the suspension
solution will effect the desired precipitation.
Alternatively, pecto-cellulosic product is recovered without the addition
of alcohol, but by adjusting the pH and drying the slurry comprising the
hydrolyzed pectin. The pH is adjusted to a more neutral pH, typically the
pH of the mixture before the addition of acid. This will usually be in the
range of about 3 to 4, typically about 3.5.
The process of first solubilizing the pectin present in the cellulose
matrix of the citrus peel and recovering the pectin without separating the
cellulosic components has been found to provide an "activated"
"pecto-cellulosic" composition which possesses enhanced activity as a
gelling agent. As demonstrated in the Experimental section hereinafter,
when used as a gelling agent in certain food products, the
pecto-cellulosic product of the present invention provides a higher degree
of gelling than commercial pectin based on the actual weight of pectin
utilized. The weight of the pecto-cellulosic product, of course, is
greater than the weight of commercial pectin used since the product
contains a significant weight percent of cellulose and other non-pectin
materials, such as hemicelluloses.
The present invention does not necessarily rely on substantial separation
of either the cellulose matrix or the liquid phase solution containing the
cellulized pectin to produce the final product. Such lack of separation is
contrary to previous methods for preparing commercial pectin where the
liquid phase containing the soluble pectin is separated from solid phase
components of the citrus peel or other vegetable source prior to
precipitation of the pectin from the liquid phase. The pecto-cellulosic
produce of the present invention be obtained by simply adjusting the pH or
precipitating the solubilized pectin back into the cellulosic matrix. Of
course, it may be possible to remove minor portions of either the
cellulosic material or the solubilized pectin in order to either increase
or decrease the final pectin content of the pecto-cellulosic product. It
would also be possible to introduce additional pectin, such as commercial
pectin, into the solubilized pectin solution in order to enhance the
pectin content of the final pecto-cellulosic product.
If alcohol precipitation is used, the acid or base will be removed with
successive alcohol washes, and the pH of the solids will be finally
adjusted using a food grade base or acid, such as sodium bicarbonate
(NaHCO.sub.3) or phosphoric acid, so that 1% by weight solutions of the
final dried pecto-cellulosic product in deionized water will have a pH in
the range from about 3 to 4, preferably being about 3.5.
After the alcohol washes are complete, the pecto-cellulosic material will
be dried in an oven and/or under vacuum and, optionally, the alcohol
vapors will be collected, recovered, and recycled. The resulting dried
pecto-cellulosic product is then comminuted to a size sufficiently small
so that it may be added directly to many food products without an
undesirable effect on texture. Typically, the final product will be ground
to a size below about 80 mesh, preferably being below about 100 mesh.
If the pecto-cellulosic product is recovered by adjusting the pH, without
the use of alcohol, the solution is also pureed to produce a fine particle
size, usually less than about 300 .mu.m, preferably less than about 200
.mu.m, and more preferably less than about 150 .mu.m. The solution can be
pureed using standard equipment such as a BEPEX-RIETZ Angle Disintegrator,
URSCHEL Comitrol, and the like. A pureeing step during hydrolysis can also
be used with the alcohol precipitate method, as well.
The pureed product is then dried using standard equipment such as spray or
drum dryers. Spray dryers such as a Damrow Filtermat spray dryer or a
BEPEX-UNISON pulse combustion spray dryer are generally preferred. The
resulting dried pecto-cellulosic product is then ground to an appropriate
size, blended and packaged.
In yet other embodiments, two products are made, a pecto-cellulosic product
with less pectin and a pectin product. In these methods, the liquid from
the initial hydrolysis slurry is separated and used to produce a purified
pectin product. The liquid can be separated using a hydrosieve,
centrifugation and other well known methods. The pectin in the liquid
phase can be used as is or precipitated. If desired, the liquid phase can
be concentrated by means well known in the art, such as ultrafiltration
and evaporation. The pectin in the solid phase can be separately
precipitated or pH adjusted and dried as described above.
The process of the present invention can also be performed in a batch mode
or a continuous manner. Referring to FIG. 1, raw citrus peel is first
ground and washed in a counter-current water flow to efficiently remove
unwanted soluble salts. The washed peel is then mixed concurrently with
water and acid to hydrolyze the protopectin. The peel/water/acid slurry is
pre-mixed in a first-in/first-out cycle with spent acid-alcohol from a
two-stage counter-current alcohol wash system. The first stage
acid-alcohol wash helps to purify the peel and to control the soluble
pectin DM. The second stage neutral alcohol wash continues the
purification while removing residual acid and allows for final product pH
adjustment. The drained alcohol peel particles containing the soluble
pectin are vacuum dried in a two-step process to recover the alcohol for
reuse and to preserve the pectin quality. All spent alcohol streams are
collected and distilled to recover alcohol and to reuse as much of the
waste acid as is practical.
Referring to FIG. 2, the process which lacks alcohol precipitation is
shown. Here, raw citrus peel is first ground and washed as described
above. The washed peel is then mixed concurrently with water and
phosphoric acid (0.6% wt % phosphoric acid) to hydrolyze the protopectin.
The slurry is allowed to hydrolyze at ambient temperature for 16-24 hours.
This step may be followed by hot hydrolysis at about 85.degree. C. The
product is then pureed and the pH is adjusted to about 4.5 using water and
sodium bicarbonate (5% w/v). Pureed product is then spray dried, ground,
blended and packaged.
FIG. 3 shows a third embodiment in which the solid and liquid phases are
separated resulting in two final products, a pecto-cellulosic and pectin,
respectively. The liquid phase is preferably first concentrated prior to
the drying step.
In other embodiments (FIG. 4), the comminuted material may be lixivated to
first partially extract soluble salts and other undesirable compounds from
the slurry. Removal of calcium ions is useful to increase solubility of
the pectin. Lixivation may be carried out using any of the acids noted
above. For example, HNO.sub.3 can be added to lower the pH of the solution
to about 1.4 to 1.6. Additional liquid is then removed by separation and
the remaining slurry is further hydrolyzed at elevated temperatures as
described above. The pH of the slurry is then adjusted, followed by drying
to produce a pecto-cellulosic product.
The pectin and pecto-cellulosic compositions prepared as just described are
suitable for incorporation into a wide variety of food and other products
requiring a gelling activity in the aqueous phase of the product, such as
food and other products which have previously used commercial pectin.
Exemplary food products which may utilize the pecto-cellulosic
compositions of the present invention include all food products in which
pectin is used such as bread doughs, fruit for yogurt, yogurt, jams, fruit
spreads, confections, and the like.
The following examples are offered by way of illustration, not by way of
limitation.
EXPERIMENTAL
EXAMPLE 1
Process with Alcohol Precipitation
Various samples of citrus peel were evaluated. Each citrus peel sample was
first ground through 1/4 inch holes in a meat grinder and separated into
2,000 gm aliquots. Each aliquot was rinsed three times with five liters of
tap water for five minutes before draining the wash water. The drained
peel aliquots were weighed, combined with an equal weight of tap water,
and adjusted to a pH from 1.2 to 1.5 with from 13 ml to 20 ml of 67%
nitric acid. The resulting slurry of ground citrus peel, water, and acid
was maintained for 16 to 24 hours at ambient temperature. The slurry was
then mixed with four liters of 100% isopropanol, and excess alcohol/water
was removed by draining over a screen having 1 mm openings. The remaining
solid material was rinsed with four liters of 60% alcohol, drained, rinsed
with another four liters of 60% alcohol with 25 to 30 ml of 5% (w/v)
sodium bicarbonate stirred into the slurry to partially neutralize the
solids just prior to drainage. The drained and neutralized solids were
rinsed with 2.5 liters of 100% isopropanol and the excess liquid drained.
The drained peel pieces were then dried at 50.degree. C. for 4 hours in a
hot air oven, the dried particles were ground to below 100 mesh and
analyzed. Typical analyses are set forth in Table 1 as follows.
TABLE 1
______________________________________
Pecto-cellulosic Composition Analysis
Sample Nos.
1 2 3 4 5 6 7
______________________________________
Citrus Peel
Lem- Lem- Lem- Lem- Lem- Ruby Valencia
on on on on on Grape-
Orange
fruit
Yield 8.9 11.0 10.5 10.6 7.4 8.4 14.9
(wt. %)
AGA 15.4 18.2 15.5 16.4 20.8 16.7 12.8
(wt. %)
Soluble 71.8 74.5 70.3 65.4 79.4 73.5 65.7
Pectin (DM)
Total Dietary
-- -- -- -- 85.6 82.1 80.7
Fiber
(wt %)
______________________________________
Commercial pectins are diluted with either dextrose or sucrose to control
the pectin's gel strength at 150 SAG grade. One gram of 150 SAG pectin can
gel 150 grams of sugar in a standard gel, under standard conditions (see,
Food Technology 13:496 (1959). These 150 SAG grade pectins have a pectin
content in the range from about 50 wt. % to 60 wt. % AGA in comparison to
the pectin content of from about 15 wt. % to 20 wt. %
polyanhydrogalacturonic acid (AGA) of the products of the present
invention. Strawberry jams were made using both a prepared 150 SAG grade
pectin and the pecto-cellulosic product of the present invention at
comparable usage levels. See Table 2 as follows.
TABLE 2
______________________________________
Strawberry Jam Preparation
Sample Nos.
Ingredient 1 2 3 4
______________________________________
Sugar (g) 550 550 550 550
Strawberries (g)
450 450 450 450
150 SAG pectin (g)
2.3.sup.1
-- 3.1.sup.3
--
Pecto-cellulosic (g)
-- 2.3.sup.2
-- 3.1.sup.4
Citric Acid (g)
1.25 1.25 1.25 1.2
Final Jam wt (g)
930 930 930 930
______________________________________
.sup.1 0.15 wt. % AGA in the strawberry jam
.sup.2 0.05 wt. % AGA in the strawberry jam
.sup.3 0.2 wt. % AGA in the strawberry jam
.sup.4 0.07 wt. % AGA in the strawberry jam
The jams were made by dispersing three parts of the sugar to one part of
the pectin component and dispersing the blend into crushed and pureed
strawberries. After bringing the mixture to a rolling boil with continuous
stirring, two-thirds of the remaining sugar was combined and the mixture
brought back to a boil. After adding the remaining sugar and bringing the
mixture back to a boil, the citric acid was added as a 50% wt./volume
solution. After cooking, the jams were poured into sterilized containers
and sealed.
The final products were found to be nearly comparable in color, flavor,
texture, spreadability, and perceived gel strength to regular jams.
Notably, the use of the pecto-cellulosic product achieved such comparable
results while using from about 25% to 35% of the amount of soluble pectin
utilized in the 150 SAG pectin. This equates to a reduction in actual
pectin usage (measured as AGA) of from about 65% to about 75% by weight.
EXAMPLE 2
Process without Alcohol Precipitation
Ground and washed citrus peel prepared as described above was mixed 2:1
with water and then phosphoric acid to a pH of between 2 to about 2.1.
This mixture was allowed to undergo a mild, slow, hydrolysis at ambient
temperature for about 24 hours. This process was followed by hot
hydrolysis up to 90.degree. C. for up to 3 hours. The temperature and time
of the hot hydrolysis was adjusted according to how much additional
hydrolysis was determined to be necessary.
The final hydrolysis mixture was then pureed to less than 149 microns using
a BEPEX-RIETZ Angle Disintegrator. The pH was then adjusted to the
original pH of the mixture (usually about pH 3.5) by incorporating a 5%
w/v sodium bicarbonate solution. Carbon dioxide generation in the mixture
usually increases the volume by about one third.
The wet mixture was then fed to a BEPEX UNISON pulse combustion spray dryer
where the solids were flash dried in less than about thirty seconds. If
all the pureed solids are less than about 149 .mu.m the dried particles
are also less than 149 .mu.m.
EXAMPLE 3
Saponification Method to Determine Degree of Methylation and Percent
Methoxyl, Galacturonic Acid or Polyanhydrogalacturonic Acid
General
The properties and uses of pectin to a large extent are determined by its
Degree of Methylation (DM) which is the percentage of total carboxyl
groups (COOH) in the methyl ester form (COOCH.sub.3). Methyl groups
(CH.sub.3) are removed (saponified by alkali (NaOH). In the removal,
sodium (Na) replaces CH.sub.3 (COOCH.sub.3 becomes COONa). The amount of
CH.sub.3 present is determined by how much NaOH is used up in the
saponification.
1. Determination of Degree of Methylation
The steps in the determination of DM are as follows:
1. Determine free COOH by titrating an approximate 0.5% by weight pectin
solution with 0.1N NaOH to a bromothymol blue end-point equivalent to "A"
titer.
2. Add excess 0.5N NaOH to saponify the CH.sub.3 groups.
3. Add 0.5N HCl equivalent to the 0.5N NaOH added.
4. Titrate excess HCl with 0.1N NaOH again to bromothymol blue end-point
equivalent to "B" titer.
5. DM is equivalent to the number ratio of carboxyl groups in the methyl
ester form
All carboxyls must be free of metals before the method can be applied. A
mixture of cation and anion exchange resins is stirred with the pectin
solution to remove metals. The cation exchange resin removes the metal
ions releasing an equivalent amount of acid. The anion exchange resin
picks up the released acid. The net effect is pectin purification as far
as positive and negative ions are concerned.
Equipment
Hamilton Beach Drinkmaster or similar equipment
Erlenmeyer Flasks, wide mouth, 500 and 1000 ml
Stoppers, rubber, #8 & #10 (to fit erlenmeyers)
Burettes, 25 and 50 ml with 0.10 ml graduations
Buchner funnels, 2-piece Nalgene Polypropylene, 9 cm
Filter flasks, 500 ml
Wash bottle
Whatman Filter Paper, 9 cm, #113
Reagents
Amberlite Ion Exchange Resin, MB-1 or IRN-150 (Rohm and Haas)
Sodium Hydroxide (NaOH) Pellets, Reagent grade
Hydrochloric Acid (HCl), Reagent Grade
Bromothymol Blue
Isopropanol, Reagent Grade
Deionized or Distilled Water
Solutions
0.1 and 0.5N NaOH
0.5N HCl
Bromothymol Blue indicator, 1 g/100 ml in 50%
Isopropanol
Procedure
1. Prepare a one percent by weight solution of ground sample in deionized
water (i.e., 4 gms and 396 gms water). Disperse in the water using the
"Drinkmaster". Agitate rapidly until all ground particles are dispersed.
2. After solubilization of the pectin, add about 35 gms MB-1 resin and
continue agitation at slow speed for a minimum of 10 minutes.
3. Filter through #113 Whatman paper using the Buchner funnel.
4. Transfer aliquots of the filtrate into either the 500 or 1000 ml
Erlenmeyer flasks depending upon sample size. Dilute with deionized water
to an approximate half percent solution.
5. Add 10 drops bromothymol blue indicator and titrate with 0.1N NaOH to a
blue end-point that persists for 30 seconds with constant swirling ("A"
titer, equivalent to COOH groups).
6. Add 20 mls of 0.5N NaOH, stopper and let stand one hour; then add an
equivalent amount of 0.5N HCl. Mix well after each addition.
7. Titrate again to the 30 second blue end-point with 0.1N NaOH ("B" titer,
equivalent to COOCH.sub.3 groups).
##EQU1##
2. Determination of Percent Methoxyl; Galacturonic Acid or
Polyanhydrogalacturonic Acid
The same procedure can be followed to determine percent methoxyl
(OCH.sub.3), galacturonic acid (GA) and polyanhydrogalacturonic acid (AGA)
content. Steps have to be taken to keep the method quantitative. Resin
treat known solution weights and then quantitatively transfer the
solutions as follows:
1. Thoroughly rinse from one container to the other with deionized water.
2. When filtering to separate the resin wash with three 20 ml portions of
boiling deionized water.
It is not necessary to use standardized 0.5N NaOH and HCl solutions.
Determine their equivalence by volume ratio.
It is necessary to standardize the 0.1N NaOH when percent OCH.sub.3 and GA
are wanted. Unstandardized 0.1N NaOH can be utilized for a simple DM
analysis provided the same solution is used in both the A and B titrations
as the DM is based upon only a calculated ratio.
Calculations:
##EQU2##
Although the foregoing invention has been described in detail for purposes
of clarity of understanding, it will be obvious that certain modifications
may be practiced within the scope of the appended claims.
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